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[dragonfly.git] / secure / lib / libcrypto / man / rc4.3
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138.\" ======================================================================
139.\"
140.IX Title "rc4 3"
141.TH rc4 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144RC4_set_key, \s-1RC4\s0 \- \s-1RC4\s0 encryption
145.SH "SYNOPSIS"
146.IX Header "SYNOPSIS"
147.Vb 1
148\& #include <openssl/rc4.h>
149.Ve
150.Vb 1
151\& void RC4_set_key(RC4_KEY *key, int len, const unsigned char *data);
152.Ve
153.Vb 2
154\& void RC4(RC4_KEY *key, unsigned long len, const unsigned char *indata,
155\& unsigned char *outdata);
156.Ve
157.SH "DESCRIPTION"
158.IX Header "DESCRIPTION"
159This library implements the Alleged \s-1RC4\s0 cipher, which is described for
160example in \fIApplied Cryptography\fR. It is believed to be compatible
161with RC4[\s-1TM\s0], a proprietary cipher of \s-1RSA\s0 Security Inc.
162.PP
163\&\s-1RC4\s0 is a stream cipher with variable key length. Typically, 128 bit
164(16 byte) keys are used for strong encryption, but shorter insecure
165key sizes have been widely used due to export restrictions.
166.PP
167\&\s-1RC4\s0 consists of a key setup phase and the actual encryption or
168decryption phase.
169.PP
170\&\fIRC4_set_key()\fR sets up the \fB\s-1RC4_KEY\s0\fR \fBkey\fR using the \fBlen\fR bytes long
171key at \fBdata\fR.
172.PP
173\&\fIRC4()\fR encrypts or decrypts the \fBlen\fR bytes of data at \fBindata\fR using
174\&\fBkey\fR and places the result at \fBoutdata\fR. Repeated \fIRC4()\fR calls with
175the same \fBkey\fR yield a continuous key stream.
176.PP
177Since \s-1RC4\s0 is a stream cipher (the input is XORed with a pseudo-random
178key stream to produce the output), decryption uses the same function
179calls as encryption.
180.PP
181Applications should use the higher level functions
182EVP_EncryptInit(3)
183etc. instead of calling the \s-1RC4\s0 functions directly.
184.SH "RETURN VALUES"
185.IX Header "RETURN VALUES"
186\&\fIRC4_set_key()\fR and \fIRC4()\fR do not return values.
187.SH "NOTE"
188.IX Header "NOTE"
189Certain conditions have to be observed to securely use stream ciphers.
190It is not permissible to perform multiple encryptions using the same
191key stream.
192.SH "SEE ALSO"
193.IX Header "SEE ALSO"
194blowfish(3), des(3), rc2(3)
195.SH "HISTORY"
196.IX Header "HISTORY"
197\&\fIRC4_set_key()\fR and \fIRC4()\fR are available in all versions of SSLeay and OpenSSL.